BTW, Elco is not the first town to get an acronymic name. There’s a fair number of towns where the namers took the initials of several people and composed a name from them. There’s a list of them here (way down on the same page as the one in the OP).
The earliest of those I could find is Le Mars, Iowa, named in 1870. Here’s a description of how they came up with the name:
However, that’s not the earliest place name acronym I could find. There’s an Omphghent Township in Madison County, Illinois. The name is combination of an acronym: Our Mother of Perpetual Help = OMPH plus Ghent, the city in Belgium. This was named in 1858. cite